Multiple concentric electrode gap construction



MULTIPLE CONCENTRIC ELECTRODE GAP CONSTRUCTION Filed March 16, 1953Inventors: Donald W. Crouch, James H. SnelLJr.

Thomas J. Carpenter, b5 vim/Q MM? Their Attorneg.

United States Patent MULTIPLE CONCENTRIC ELECTRODE GAP CONSTRUCTIONDonald W. Crouch, Ancramdale, N. Y., and James H. Snell, Jr., and ThomasJ. Carpenter, Pittsfield, Mass, assignors to General Electric Company, acorporation of New York Application March 16, 1953, Serial No. 342,522

4 Claims. (Cl. 313268) This invention relates to a multiple concentricelectrode gap construction, and more particularly, to a multipleconcentric electrode gap construction suitable for incorporation intolightning arresters for the interruption of high power follow currents.

In some of the prior known gap unit constructions for lightningarresters a pair or plurality of gap electrodes are positioned betweentwo insulating plates. Once an arc is struck across the electrodes ofthe gap unit an arc is continuously maintained at a relatively fixedposition with respect to the gap unit parts. This is undesirable. Forinstance, with a fixed arc metallic vaporization of the electrodes mayoccur as well as a burning of the insulating plates. Also, since the arcis fixed, the conduction of heat from the arc by the electrodes andinsulating plates is relatively limited. These factors limit themagnitude of the power follow currents that can be interrupted.

It is an object of this invention to provide a gap unit constructionwhereby the are within the gap unit is continuously moving with respectto the gap unit parts.

Our invention comprises a multiple concentric electrode gap unitcomprising a plurality of narrow ringlike concentric spaced metallicelectrodes positioned between two electrical insulating material plates.

Our invention further comprises the combination of magnetic means and amultiple concentric electrode gap unit, said unit comprising a pluralityof annular narrow concentric spaced metallic electrodes positionedbetween two electrical insulating material plates, whereby the magneticfield of the magnetic means transverse to the plane of the insulatingplates will react with the magnetic field produced by a radial arcstruck across said electrodes to cause said are to continuously rotatewithin said gap unit.

The invention will be better understood by considering the followingdescription taken in connection with the accompanying drawing and itsscope will be pointed out in the appended claims.

In the drawing, Figure 1 is a view of a lightning arrester assemblyembodying our invention. Figure 2 is a view in section of our multipleconcentric electrode gap unit with a magnetic means cooperativetherewith. Figure 3 is an exploded view in perspective of the multipleconcentric electrode gap unit parts and magnetic means of Figure 2. Likereference numerals throughout the various figures indicate like parts.

Referring particularly to Figure 1, shown therein is a weather prooflightning arrester assembly embodying our invention comprising aninsulating material, as porcelain, housing 1 enclosing a plurality ofstacked gap units 2, magnetic means units 3, and non-linear resistanceunits 4. At the upper and lower ends of housing 1 are terminals 5 and 6respectively so that the assembly can be connected between a source ofelectrical energy or apparatus to be protected and ground. Positionedbetween terminal 5 and uppermost magnetic means unit 3 is an electricalconducting spring 7 and contact plate 8. Spring 7 ensures goodelectrical contact between the various stacked gap, magnetic means, andnon-linear resistance units and the terminals.

Referring particularly to Figures 2 and 3, shown there in are thedetails of one of the gap units 2 and one of the magnetic means units 3.The gap unit 2 comprises a thin cup-like outer metallic electrode 9which receives a non-gas evolving electrical insulating material plate13. The insulating material plate 13 has an annular ridge 10 formed onits upper surface adjacent to but spaced from its outer circumference.The ridge 10 has positioned within its inner and about its outercircumference two narrow annular intermediate metallic electrodes 11 and12 respectively. Obviously, more elec trodes can be added merely by theformation of additional ridges on the upper surface of insulatingmaterial plate 13. Positioned above and opposite parts 9 to 13 is anon-gas evolving electrical insulating material plate 14. On the uppersurface of insulating material plate 14 is a metallic contact plate 15.Positioned on the under surface of the insulating material plate 14 isan annular metallic electrode 16 spaced with respect to the uppersurface of insulating material plate 13. Plate 15 and electrode 16 arein electrical contact and insulating material plate 14 is firmly clampedtherebetween by connecting portion 17.

The two insulating plates 13 and 14 define therebetween a shallow arcchamber or space with the multiple concentric annular or ring-likeelectrodes positioned therein. The height or width of the electrodes 11,12, and 16, and of the lip of the cup-like electrode 9 is considerablyless than their diameters. The underside of the insulating plate 14 hasa plurality of radially extending narrow ridges 18 formed thereondefining a plurality of grooves or vents 19 therebetween. Thus, whenplate 14 is positioned opposite plate 13 the arc chamber or air spacetherebetween will be vented by grooves or vents 19.

Formed on the ridges 18 adjacent the circumference of plate 14 are cupcentering ridges 20. That is, ridges 20 center the cup electrode 9, plusthe electrodes 11 and 12 concentrically with respect to inner electrode16. The electrodes 11, 12, and 16 as Well as the lip of cup electrode 9are positioned within the arc chamber defined by the spaced insulatingplates 13 and 14. The base of cup 9 serves to make electrical contactwith an adjacent gap unit or non-linear resistor as shown in Figure 1.Every adjacent pair of electrodes defines an annular unobstructed airgap therebetween so that when an arc is struck within the gap unit therewill be a plurality of radial electrically series connected arcstherein. As will appear later, deionization is produced when the arcsare swept or rotated between and against the non-gas evolving walls ofthe insulating material plates. The insulating material plates may be ofeither porous or impermeable material.

The magnetic means unit 3 is not our invention but is a circularadaptation of the magnetic means unit disclosed in the copendingapplication of Arthur A. Olsen and Wilfred F. Skeats, Serial No. 185,994filed September Zl, 1950, now Patent No. 2,644,116 issued June 30, 1953and assigned to the same assignee as the instant application. Themagnetic means unit 3 has a circular spool 21 with an electric coil 22thereabout. The ends of said coil 22 are attached to conductor plates 23resting on ledges 24 formed within the inner circumference of spool 21.The conductor plates 23 are spaced by mica sheets 25 and definetherebetween coil shunting gap 26. The conductor plates 23 are clampedto ledges 24 and the ends of the coil 22 attached to said conductorplates by virtue of contact eyelets 27.

When the magnetic means unit 3 and gap unit 2 are stacked together thecontact plate of gap unit 2 will make electrical contact with one of thecontact eyelets 27. The plate 15 is correctly proportioned to fit withinthe inner circumference of spool 21' to make this electrical contact andauxiliary ledges 28 help steady the coil and gap units with respect toeach other to make good electrical contact in a compact fashion.

As will be readily apparent to those skilled in the art, coil winding 22is electrically connected in series with gap unit 2, and shunting gap 26provides a by-pass or shunt around the winding 22 for its protectionduring the passage of a transient having components with rapid rates ofcurrent change. Following the establishment of a plurality ofelectrically series connected arcs within gap unit 2 and dissipation ofthe transient, the power follow current path to ground will include thewinding 22 so that the magnetic field produced thereby within theperiphery of the coil 22 transverse to the planes of the insulatingplates 13 and 14 will react with the magnetic field produced by thecurrent in the radial arcs struck across the multiple concentricelectrodes 16, 11, 12, 9 to rotate said arcs. Since said arcs arecontinuously rotating within the shallow confines of the arc chamberbetween insulating plates 13 and 14, said arcs are continuously incontact with the adjacent cool surfaces of the plates 13 and 14. Also,since the arcs are continuously rotating there is little opportunity formetallic vaporization or localized erosion of the electrodes orinsulating plates. The arcs can strike along any radial path. With thisconcentric design of the electrodes of the gap unit and continuousrotation of the arcs maximum use of the deionizing surfaces of theinsulating material plates is attained. With a greater degree of coolingof the arcs and deionization the range of power follow currents that canbe interrupted are accordingly higher. With a higher interruptingcapacity gap unit the resistance of the valve elements or non-linearresistances 4 of Figure 1 can be reduced to provide lower arresterprotective levels.

Our gap unit construction also gives control of the gap unit sparkovervoltage. The potentials of the intermediate electrodes 11 and 12 arecontrolled by the electro-static field distribution through theinsulating plates 13 and 14 from contact plates d and 15. Ccnsequently,the current interrupting ability of the gap unit can be increasedwithout affecting the voltage sparkover of the gap unit by increasingthe gap spacings defined by electrodes 9, 11, 12, and 16 due to thecontrol of the potentials of the intermediate electrodes 11 and 12 bythe design of the insulating plates 13 and 14 which controls theelectro-static field potentials.

An additional advantage of our invention is the compactness andsimplicity of the gap unit. There is an efficient use of space and.materials. Costs are radically reduced over the costs of other gapunits of comparable interrupting capacity. Also, each gap unit iscompactly enclosed to prevent flashover between stacked units withadequate venting of each gap unit. Additional electrodes in betweeninner electrode 16 and outer electrode 9 break the large gaptherebetween into a series of small annular concentric unobstructed gapsto give a plurality of electrically series connected arcs without anyappreciable elongation thereof. With proper cooling of the arcs anddeionization there is no opportunity for the arcs to restrike.

Whilethere has been shown and described a particular embodiment of theinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention, andthat it is intended by the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. A gap construction comprising two circular electrical insulatingplates, one of said plates positioned in the bottom of a shallowcup-like metallic electrode, the lip of said cup-like electrodeprotruding beyond the upper surface of said one plate, the other of saidplates positioned above said one plate and cup lip, said two platesdefining a shallow arc chamber therebetween, a centermost metallicelectrode protruding through the center of said other plate into saidchamber in spaced relationship with respect to said one plate, the lipof said cuplike electrode and said centermost electrode concentricallydisposed with respect to each other defining an annular circular air gaptherebetween, the depth of said shallow arc chamber being considerablyless than the diameter of said lip.

2. A gap construction as in claim 1, wherein a narrow intermediatemetallic electrode is positioned Within said chamber between saidcentermost electrode and said lip, said lip, intermediate, andcentermost electrodes being concentrically disposed with respect to eachother where by said annular circular air gap is divided into a pluralityof electrically series connected annular circular air gaps, saidintermediate electrode being spaced from said centermost electrode andsaid lip.

3. A gap construction comprising two circular electrical insulatingplates, one of said plates positioned within the bottom of a thincup-like metallic element, the lip of said cup-like element protrudingbeyond the upper surface of said one plate and constituting an outermostelectrode, said one plate upper surface having a shallow annular ridgeformed thereon between the center and periphery of said one plate,annular narrow intermediate metallic electrodes positioned within andabout the inner and outer periphery of said ridge, the upper edges ofsaid intermediate electrodes protruding beyond the upper edge of saidridge, the other of said insulating plates superimposed with respect tosaid lip and upper edges, said insulating plates defining a shallow arcchamber therebetween, a centermost metallic electrode protruding throughthe center of said other plate into said chamber in spaced relationshipwith respect to said one plate upper surface and centrally disposed withrespect to said lip and intermediate electrodes, contact means on theupper surface of said other plate making electrical contact with saidcentermost electrode, all of said electrodes concentrically disposedwith respect to each other and defining therebetween a plurality ofconcentric annular circular unobstructed air gaps, the lower surface ofsaid cup like element bottom constituting a second contact means.

4. A multiple gap unit comprising two superposed elec trical insulatingplates closely spaced with respect to each other and defining'a shallowarc chamber therebetween, at least three shallow ring-like metallicelectrodes concentrically disposed and spaced with respect to each otherReferences Cited in the file of this patent UNITED STATES PATENTS MayJune 30, 1914 Tezner Oct. 4, 1949 OTHER REFERENCES Wade: Abstract ofapplication Serial No. 635,316, publi'shed October 4, 1949.

